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.Management Sciences
Category: Electrical Engineering Materials
Platinum is used in_____________?
A. electrical contacts
B. thermocouple
C. heating element in high temperature furnace
D. grids of special purpose vacuum tubes
E. all of the above
The covalent bond is formed by_______________?
A. transfer of electrons between atoms
B. sharing of electrons between atoms
E. sharing of variable number of electrons by a variable number of atoms
D. none of the above
Due to which of the following factors the brush wear rate is altered ?
A. Speed of the machine
B. Contact pressure
C. Surface conditions of brush and commutator
D. Excessive sparking
E. All of the above
Due to which of the following reasons aluminium does not corrode in atmosphere ?
A. Aluminium is a noble metal
B. Atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of aluminium
C. No reaction with oxygen occurs ft Any of the above
The conductivity of a conductor can be increased by_______________?
A. decreasing its temperature
B. increasing its temperature
C. decreasing its vibration
D. increasing its vibration
Surface resistance of an insulating material is reduced due to the______________?
A. smoky and dirty atmosphere
B. humidity in the atmosphere
C. both (A) and (b)
D. neither (A) nor (b)
In graphite, bonding is____________?
A. covalent
B. metallic
C. Vander Waals
D. Vander Waals and covalent
A highly conductive material must have___________?
A. highest conductivity
B. lowest temperature co-efficient
C. good mechanical strength
D. good corrosion resistance
E. easy solderable and drawable quality
F. all of the above
The photo-electric effect occurs only when the incident light has more than a certain critical____________?
A. intensity
B. speed
C. frequency
D. wave length
The conduction of electricity, in semiconductors, takes place due to movement of______________?
A. positive ions only
B. negative ions only
C. positive and negative ions
D. electrons and holes
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